When all nutrients have been absorbed, water, bacteria, and fiber pass through the ileocecal valve to the large intestine or colon. The ileocecal valve is located by your right hipbone and separates the contents of the small and large intestine. The appendix is a small, fingerlike sac that extends off the beginning of the colon.

Until recently, the function of the appendix was a mystery. Now we know it contains a great deal of lymphatic tissue and is thought to be part of the immune system. The colon is short—only three to five feet long. Its job is to absorb water and remaining nutrients from the chyme and form stool.

Two-and-a-half gallons of water pass through the colon each day, two-thirds of which come from body fluids. The efficient colon pulls 80 percent of the water out of the chyme, which is absorbed into the bloodstream.

The large intestine has three main parts: the ascending colon (up the right side of the body), the transverse colon (straight across the belly under the ribs), and the descending colon (down the left side of the body) to the rectum, where feces exit the body. Stool begins to form in the transverse colon.

If the chyme passes through the colon too quickly, water is not absorbed, causing diarrhea. Stool that sits too long in the colon becomes dry and hard to pass, leading to constipation. About two-thirds of stool is composed of water and undigested fiber and food products. The other third is composed of living and dead bacteria.

The large intestine contains trillions of bacteria. Helpful bacteria, called flora, lower the pH of the colon, killing disease-causing microbes. Intestinal flora also produce vitamins B and K, protect us from illness, enhance peristalsis, and make lactase for milk digestion.

When the stool is finally well formed, it gets pushed down into the descending colon and then into the rectum. It is held there until there is sufficient volume to have a bowel movement. Two sphincters—rings of muscle—control bowel movements. When enough feces have collected, the internal sphincter relaxes and your mind gets the signal that it’s time to relieve yourself.

The external sphincter opens when you command it. Because this is voluntary, you can have the urge to defecate, but wait until it’s convenient. If you ignore the urge, water keeps being absorbed back into the body and the stool gets dry and hard. Some people are chronically constipated because they don’t want to take the time to have a bowel movement or don’t like to have bowel movements at work.

We can learn a lot about ourselves from stool. Dennis Burkitt, M.D., father of the fiber theory, found that on average people on Western diets excreted only five ounces of stool daily, whereas Africans eating traditional diets passed sixteen ounces. Wellformed stool tells us when it wants to come out; we don’t need to coax it.

It looks like a brown banana with a point at one end, is well-hydrated, and just slips out easily. Stool that looks like little balls all wadded together has been in the colon too long. The longer waste materials sit in the colon, the more concentrated the bile acids become; concentrated bile acids irritate the lining of the colon.

Hormones that have been broken down by the body are also excreted via our feces. If the stools sit in the colon for too long, these hormones are reabsorbed into the bloodstream, increasing the risk for estrogen-dependent cancers. Betaglucuronidase, an enzyme that may indicate formation of cancercausing substances in the colon, can be measured as a marker of hormone reabsorption.

Frequency of bowel movements is a good health indicator. How often do you have a bowel movement? People on good diets generally have one to three each day. If you are not having a daily bowel movement, there can be many causes.

First, take a close look at your diet. You probably aren’t eating enough fiber. If not, increase your intake of fruits, vegetables, whole grains, and legumes. These foods are generally high in magnesium, which helps normalize peristalsis. Make sure that you are drinking enough fluids.

Coffee and soft drinks don’t count. And get regular exercise. Second, a good indicator of your colon’s health is your bowel transit time—how long it takes food to move from the first swallow until it exits the body. When your system is working well, the average amount of time is twelve to twenty-four hours.

On average, Americans have a transit time that is way too long—forty-eight to ninety-six hours—because we don’t eat enough highfiber foods or drink enough water. You can do a simple home test to determine your transit time, which gives you important information about the way your body works.

Let’s take a look at which foods you are eating and begin the process of cleaning up your diet. Take last week’s diary and get out some crayons or markers—you’re going to color.

Look at those circles. Is there one food group that dominates your diary? If you eliminated one of these categories from your diet, which would be the easiest to give up and which would be the most difficult? Sometimes, the ones that are the hardest to give up are the ones that are causing us the most trouble.

They temporarily make us feel better, even though they are really making us sicker. Why? Our bodies react negatively to cigarettes, dairy products, caffeine, sugar, wheat, pork, beef, citrus fruits, or any other foods, yet we crave them.

This week, focus on the foods you circled in red and eliminate all the sweets. Sugars ferment and can contribute to your digestive problems. Get rid of soft drinks, cookies, pastries, donuts, and sugar added to coffee or tea. We’re not talking about perfection here. Let’s just make some progress.

Next week, eliminate other items circled in red. Foods with hydrogenated oil or vegetable shortening, for example, may be a good pick. Keep reworking your diet until 90 percent or more of your food choices are optimal!